Polyethylene terephthalate resin compositions

ABSTRACT

A polyethylene terephthalate resin composition capable of providing a molded article of a high crystallinity and an excellent dimensional stability and thermal resistance consists essentially of a polyethylene terephthalate resin having an intrinsic viscosity of 0.35 to 0.9 and, per 100 parts by weight of the polyethylene terephthalate resin, 5 to 200 parts by weight of an inorganic filler, 0.01 to 20 parts by weight of dimethyl or diethyl terephthalate and 0.01 to 5 parts by weight of a salt of a carboxylic acid with a metal of Group I or II in the periodic table or 0.1 to 10 parts by weight of an ionic copolymer of an α-olefin with a salt of an α,β-unsaturated carboxylic acid and containing an ion of a metal of Group I or II in the periodic table.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a polyethylene terephthalate resin composition.More particularly, the invention relates to a polyethylene terephthalateresin composition of a high crystallinity and excellent in moldabilityand in dimensional stability.

2. Description of the Prior Art

Polyethylene terephthalate resins have excellent properties, such asmechanical properties, chemical resistance, electrical properties andheat resistance, and are widely utilized for electrical insulatingmaterials, automobile parts and the like. These properties ofpolyethylene terephthalate resins can be improved by the addition ofvarious additives, such as a fiber reinforcement, e.g. glass fiber orcarbon fiber, a function-imparting agent, e.g. flame retarder, and thelike, and thus, the use of polyethylene terephthalate resins hasincreasingly been broadened.

Polyethylene terephthalate resins belong to crystalline resins and arecharacterized in that their properties largely depend upon thecrystallinity thereof. Therefore, it is necessary to highten theircrystallinity in order to improve the dimensional stability anddeflection temperature thereof. Thus, there has been proposed variousmeans for accelerating the crystallization of polyethylene terephthalateresins. For example, there have been proposed a method in which a moldedarticle obtained in a partially crystallized state is subjected topost-heat treatment to further the crystallization process and a methodin which such a molded article is dipped into a liquid capable ofenhancing the crystallinity. However, these methods undesirablynecessitate some post-treatments and have a further drawback in that themolded article may be deformed upon the post-treatment.

Further, there has been known a method in which, in order to acceleratethe crystallization of a resin at the time of the fabrication, themolten resin is injected into a mold heated to a high temperature andthen hardened within the mold. In this method, the use of a heatingmedium is necessary to maintain the mold at a high temperature, which isundesirable from the point of view of safety in the molding operation,and further, a long molding cycle time is required.

Recently, nucleating agents have been used for shortening the moldingcycle time. Although such a method can afford a high crystallinity in afairly short period of time, there is still room for improvement. Forexample, even in the case where a nucleating agent is added to apolyethylene terephthalate resin, it is necessary to use a mold of ahigh temperature, such as 130° to 140° C. In British Pat. No. 2,015,014,it is described that the use of a crystal growing agent in combinationwith a crystal nucleating agent can successfully lower the moldtemperature to a fair extent. However, this method also leaves room forimprovement in that the proposed crystal growing agent used is necessaryin a fairly large amount and, thus, the properties inherent to thepolyethylene terephthalate resin may deleteriously be affected.

SUMMARY OF THE INVENTION

It has now been found that the incorporation of specific amounts ofdimethyl terephthalate or diethyl terephthalate and a specific metalsalt of a carboxylic acid or a specific ionic copolymer into apolyethylene terephthalate resin can advantageously attain thesuccessful molding of an article in a mold of a temperature of 85° to110° C. and, thereby, provide a molded article of an excellentdimensional stability and thermal resistance.

Thus, it is the primary object of the present invention to provide apolyethylene terephthalate resin composition capable of providing amolded article of excellent properties by molding it at a moldtemperature of 85° to 110° C.

The above and other objects, which will become apparent from thedescription hereinbelow, can be attained by a polyethylene terephthalateresin composition according to the present invention, which comprises:(A) a polyethylene terephthalate resin having an intrinsic viscosity of0.35 to 0.9 as measured in ortho-chlorophenol at 35° C., and per 100parts by weight of the polyethylene terephthalate resin; (B) 5 to 200parts by weight of an inorganic filler; (C) 0.1 to 20 parts by weight ofdimethyl terephthalate or diethyl terephthalate; and (D) 0.01 to 5 partsby weight of a salt of a carboxylic acid with a metal of Group I or IIin the periodic table or 0.1 to 10 parts by weight of an ionic copolymerof an α-olefin with a salt of an α,β-unsaturated carboxylic acid andcontaining an ion of a metal of Group I or II in the periodic table.

DESCRIPTION OF PREFERRED EMBODIMENTS

The polyethylene terephthalate resin usable as component (A) includespolyethylene terephthalates obtainable using as the acid componentterephthalic acid or an ester-forming derivative thereof and as theglycol component ethylene glycol or an ester-forming derivative thereof.However, polyethylene terephthalates obtained by replacing a portion ofthe terephthalic acid component or ethylene glycol component by acopolymerizable component may also be useful. Examples of such acopolymerizable component includes aromatic dicarboxylic acids such asisophthalic acid, phthalic acid, alkyl-substituted phthalic acids, e.g.methylterephthalic acid and methylisophthalic acid,naphthalene-dicarboxylic acids, e.g. naphthalene-2,6-dicarboxylic acid,naphthalene-2,7-dicarboxylic acid and naphthalene-1,5-dicarboxylic acid,and diphenoxyethane dicarboxylic acids, e.g.4,4'-diphenoxyethanedicarboxylic acid; aliphatic and alicyclicdicarboxylic acids such as succinic acid, adipic acid, sebacic acid,azelaic acid, decadicarboxylic acid and cyclohexanedicarboxylic acid;aliphatic and alicyclic diols such as trimethylene glycol,tetramethylene glycol, hexamethylene glycol, neopentyl glycol,diethylene glycol, 1,4-cyclohexanedimethanol; dihydroxybenzenes such ashydroquinone and resorcinol; bisphenols such as2,2-bis(4-hydroxydiphenyl)-propane and2,2-bis(4-hydroxydiphenyl)-sulfone; aromatic diols such as ether diolsobtainable from bisphenols and glycols such as ethylene glycol; and,hydroxycarboxylic acids such as ε-hydroxycaproic acid, hydroxybenzoicacid and hydroxyethoxybenzoic acid. These copolymerizable components maybe employed alone or as a mixture of two or more thereof. Preferably,they are employed in an amount of not more than 20 mol% of the totalamount of the carboxylic acid (hydroxycarboxylic acids should becalculated as a half thereof being the carboxylic acid).

The polyethylene terephthalates may have a branched chain copolymerizedwith a small proportion of a trifunctional or tetrafunctionalester-forming compounds, such as tricarballylic acid, trimesic acid ortrimellitic acid. The polyesters may be employed alone or as a mixtureof two or more thereof.

The polyethylene terephthalate resin usable for the present inventionshould have an intrinsic viscosity of 0.35 to 0.9, preferably 0.45 to0.8, as measured at 35° C. using ortho-chlorophenol as a solvent. Theuse of a polyethylene terephthalate resin of an intrinsic viscosity lessthan 0.35 provides a molded article of a low strength. If the intrinsicviscosity is more than 0.9, the resulting articles may have a lowlustrous surface appearance due to the low flowability of the resincomposition and further have unstable mechanical and thermal properties.

The inorganic filler (B) usable for the present invention includesfibrous reinforcements such as glass fiber, asbestos, carbon fiber andpotassium titanate fiber, and inorganic fillers, such as mica, silica,talc, calcium carbonate, glas bead, glass flakes, clay and wollastonite,in a powder, granular or plate form.

The dimethyl or diethyl terephthalate usable for the (C) component actsas desired, in the present invention, in combination with the carboxylicacid salt or ionic copolymer as (D) component. The terephthalate shouldbe added in an amount of 0.1 to 20 parts by weight, preferably 0.5 to 10parts by weight, per 100 parts by weight of the polyethyleneterephthalate resin. If the amount of the terephthalate added is lessthan 0.1 parts by weight, a substantial effect to accelerate thecrystallization may not be attained. In the case where the terephthalateis added in an amount of more than 20 parts by weight, the effect toaccelerate the crystallization may not be increased and the resultingmolded article may have a low strength.

The carboxylic acid salt usable for the (D) component is selected fromcarboxylic acid salts of metals of Groups I and II in the periodic tableand there may be exemplified such metal salts of aliphaticmonocarboxylic acids such as acetic acid, propionic acid, caproic acid,palmitic acid, stearic acid, oleic acid, behenic acid, montanic acid,methacrylic acid and acrylic acid, of aliphatic dicarboxylic acids suchas oxalic acid, adipic acid, succinic acid, sebacic acid, maleic acidand fumaric acid, and of aromatic carboxylic acids such as benzoic acid,terephthalic acid and phthalic acid. Suitable metals are sodium,potassium, lithium, magnesium, calcium, zinc and the like. Thesecarboxylic acid salts need no always be neutralized in all the carboxylgroups, but a part of the carboxyl groups may be in a salt form and theremaining groups may be in a free acid or ester form.

(D) component may preferably be an ionic copolymer of an α-olefin withan α,β-unsaturated carboxylic acid salt and containing an ion of a metalof Group I or II in the periodic table. Such ionic copolymers may beprepared by a known method as described, for example, in U.S. Pat. Nos.3,639,527, 3,264,272, 3,338,739 and 3,404,134.

Examples of the ionic copolymer are those polymers having the units ofthe following structural formula, ##STR1## in which R₁ is hydrogen,alkyl of 1 to 12 carbon atoms or phenyl, R₂ is hydrogen, methyl orethyl, M_(e) is a metal atom of Group I or II in the periodic table, xand y are each independently an integer of 1 to 100, and n is an integerof 10 to 10,000.

Ionic copolymers of an α-olefin and an α,β-unsaturated dicarboxylic acidsalt, for example, of ethylene and a salt of maleic acid or itaconicacid, and containing a Group I or II metal ion may also be used.

Other examples of the ionic copolymer are ionic graft copolymersobtained, for example, by grafting an α,β-unsaturated carboxylic acidester to a polyolefin, saponifying the graft polymer and then reactingit with an alkali metal hydroxide.

The above-mentioned ionic copolymers should preferably have an olefincontent of at least 50% by weight. Copolymers having an olefin contentof 80 to 99% by weight may especially be suitable.

Further examples of the ionic copolymer are those copolymers having thefollowing units (a), (b) and (c), ##STR2## in which R₁, R₂ and M_(e) areas defined above, R₃ is hydrogen, methyl or ethyl, R₄ is hydrogen oralkyl of 1 to 12 carbon atoms, and x, y and z are each independently aninteger of 1 to 100. These ionic copolymers should preferably have anolefin content of at least 50% by weight, with those having an olefincontent of 80 to 90% by weight being especially preferable. Preferably,the total content of the ester component ((c)) and the ionic component((b)) may be at least 10% by weight and the content of the ioniccomponent ((b)) may be at least 3% of the weight of the ionic copolymer.All the carboxyl groups of the ionic copolymer need not always beneutralized, but at least 10% of the carboxyl groups should beneutralized by metal ions.

Especially preferable metal ions are alkali metal ions, particularly thesodium ion. Especially preferable ionic copolymers are those of ethyleneand methacrylic acid and containing an alkali metal ion, particularlythe sodium ion.

The above-mentioned carboxylic acid salt of (D) component should beadded in an amount of 0.01 to 5 parts by weight, preferably 0.05 to 3parts by weight, per 100 parts by weight of the polyethyleneterephthalate resin. In the case where the amount is less than 0.01parts by weight, a substantial effect to accelerate the crystallizationmay not be attained. If the amount is more than 5 parts by weight, theeffect to accelerate the crystallization may not be increased and theresulting molded article may have a low strength. The ionic copolymershould be added in an amount of 0.1 to 10 parts by weight per 100 partsby weight of the polyethylene terephthalate resin. If the amount is lessthan 0.1 parts by weight a substantial effect to accelerate thecrystallization may not be attained, while if the amount is more than 10parts by weight the effect to accelerate the crystallization may not beincreased.

The polyethylene terephthalate resin composition may further havevarious additives incorporated for improving the other properties. Forexample, there may be incorporated as a flame retardant ahalogen-containing compound such as a decabromobiphenyl ether,octabromobiphenyl ether, halogenated polycarbonate oligomer (e.g.,polycarbonate oligomer obtained from brominated bisphenol A) orhalogenated epoxy compound, a phosphorus compound such as red phosphorusor triphenyl phosphate, a phosphorus-nitrogen compound such asphosphonic acid amide, or a flame-retarding auxiliary such as antimonytrioxide or zinc borate. Further, the resin composition may contain, forthe purpose of improving the thermal resistance, an antioxidant or heatstabilizer such as a hindered phenol compound, organic phosphoruscompound or sulfur compound. Furthermore, an epoxy compound may be addedto the resin composition for improving the melt viscosity stability,hydrolytic resistance or the like. As examples of such an epoxycompound, there may be mentioned a bisphenol A type epoxy compoundobtained by the reaction of bisphenol A with epichlorohydrin, analiphatic glycidyl ether obtained by the reaction of a glycol orglycerol with epichlorohydrin, a novolak type epoxy compound obtained bythe reaction of a novolak resin with epichlorohydrin, an aromatic oraliphatic carboxylic acid type epoxy compound and an alicyclic compoundtype epoxy compound obtained from an alicyclic compound, preferably abisphenol A type epoxy compound and a diglycidyl ether of alow-molecular-weight polyethylene glycol. Other additives, such asultraviolet absorbers, colorants, lubricants and foaming agents, mayalso be added as desired.

Furthermore, there may be added a small amount of another thermoplasticresin such as a styrene resin, acrylic resin, polyethylene,polypropylene, fluoroplastic resin, polyamide resin, polycarbonate resinor polysulfone; a thermosetting resin such as a phenolic resin, melamineresin, unsaturated polyester resin or silicone resin; or a softthermoplastic resin such as an ethylene-vinyl acetate copolymer orpolyester elastomer.

The polyethylene terephthalate resin composition according to thepresent invention may be prepared by any conventional blending methods.The respective components should preferably be uniformly distributedthroughout the composition. Preferably, the components may behomogeneously blended by feeding them all together or separately into amixing machine such as a blender, kneader, roll, extruder or the like.In general, the components may previously be dry mixed, the mixture thanmay be melt blended in a heated extruder and extruded into a wire shape,and finally, the extruded thread may be cut into a granular form of adesired length. The so obtained molding composition is usuallymaintained in a dry state and then submitted to molding. Alternatively,the (B) and (D) components may be added to the (A) component, before,during or after the polycondensation, in the course of the production ofthe polyethylene terephthalate resin. Thereafter, the (C) component maybe added.

The polyethylene terephthalate resin composition according to thepresent invention can provide a molded article of a very highcrystallinity that can be molded at a temperature of a broad range, andcan provide a molded article of a high excellence in dimensionalstability. The polyethylene terephthalate resin composition hasadvantageously a high flowability, as measured in an injection moldingmachine having a spiral mold.

The invention will further be illustrated by the following examples, inwhich the properties of the products were measured as follows.

(1) Deflection Temperature

This was measured according to the method of ASTM D648 under a load of264 psi.

(2) Static Strength

Tensile strength was measured according to the method of ASTM D638, andflexural strength and modulus were determined according to the method ofASTM D790.

(3) Shrinkage Factor

Injection molding was carried out using a mold having an inner dimensionof 110 mm×110 mm×2 mm, and the molding shrinkage factor and the heatshrinkage factor were calculated by the following equations: ##EQU1##

The above-mentioned molded article size is the size of a molded articleafter standing at 25° C. for 48 hours. The heat-treated article size isone of a molded article after being annealed at 130° C. for 2 hours andthen allowed to stand at 25° C. for 48 hours.

EXAMPLES 1-3 AND COMPARISON EXAMPLES 1-8

A polyethylene terephthalate resin having an intrinsic viscosity of 0.64was dried at 130° C. for 5 hours and uniformly mixed with the additivesas shown in Table 1 below, in the given proportions, in a V-type mixer.The mixture was melt blended in an extruder of a diameter of 68 mm at abarrel temperature of 270° C. and formed into pellets by cooling andcutting the thread extruded from the die.

The pellets were then hot-air dried at 130° C. for 5 hours and injectionmolded into test pieces of desired shapes at a cylinder temperature of270° C. and a mold temperature of 85° C., under an injection pressure of800 kg/cm². The cooling time was 20 seconds and the cycle was completedover a period of 35 seconds.

The obtained results are also shown in Table 1.

                                      TABLE 1                                     __________________________________________________________________________           Composition (parts by weight)  Properties of molded article                   (A)                            De-         ****                               component                      flection                                                                          Mold-   Sur-                               Poly- (B)            (D) component                                                                           tem-                                                                              ing Heat                                                                              face                               ethylene                                                                            component      Na Na Na***                                                                             pera-                                                                             shrink-                                                                           shrink-                                                                           ap-                                                                              Tensile                                                                            Flexural            Example                                                                              teleph-                                                                             Glass  (C) component                                                                         stea-                                                                            ben-                                                                             mon-                                                                              ture                                                                              age age pear-                                                                            strength                                                                           strength            No.    thalate                                                                             fiber                                                                             Talc                                                                             DMT*                                                                              DET**                                                                             rate                                                                             zoate                                                                            tanate                                                                            (°C.)                                                                      (%) (%) ance                                                                             (kg/cm.sup.2)                                                                      (kg/cm.sup.2)       __________________________________________________________________________    Comparison 1                                                                         100   --  -- --  --  -- -- --  70  0.4 1.6 x   600 1000                Comparison 2                                                                         70    30  -- --  --  -- -- --  72  0.5 1.6 x  1500 2100                Comparison 3                                                                         69.7  30  -- --  --  -- -- 0.3 74  0.5 1.6 x  1500 2100                Comparison 4                                                                         69.9  30  -- --  --  0.1                                                                              -- --  74  0.5 1.6 x  1500 2100                Comparison 5                                                                         69.9  30  -- --  --  -- 0.1                                                                              --  74  0.5 1.6 x  1500 2100                Comparison 6                                                                         67    30  -- 3   --  -- -- --  73  0.5 1.6 x  1500 2100                Comparison 7                                                                         67    30  -- --  3   -- -- --  74  0.5 1.6 x  1500 2100                Comparison 8                                                                         48.9  30  -- --  21  0.1                                                                              -- --  215 1.2 0.14                                                                              o  1200 1900                1      66.9  30  -- 3   --  0.1                                                                              -- --  212 1.3 0.13                                                                              o  1500 2100                2      71.9  25  -- --  3   0.1                                                                              -- --  211 1.3 0.13                                                                              o  1500 2100                3      63.9  20  15 --  1   -- 0.1                                                                              --  200 1.4 0.12                                                                              o  1200 1500                __________________________________________________________________________     *DMT: Dimethyl terephthalate                                                  **DET: Diethyl terephthalate                                                  ***Na montanate is based on a partial salt of a mixture of aliphatic          carboxylic acids of 22 to 32 carbon atoms.                                    ****X: Flow pattern is observed. o: Flow pattern is not observed.        

It is apparent from Table 1 that the absence of either the (C) componentor the (D) component provides a molded article of a low crystallinityand an inferior surface appearance. On the contrary, a molded articlehaving both the (C) component and the (D) component incorporated thereinin combination has a high crystallinity, a high deflection temperature,a low shrinkage factor, and a good surface appearance.

EXAMPLES 4-9 AND COMPARISON EXAMPLES 9-11

The procedure as described above was repeated using a polyethyleneterephthalate resin (A) having an intrinsic viscosity of 0.65, and aninorganic filler (B), a crystal growing agent (C) and a crystalnucleating agent (D) as shown in Table 2 below.

The obtained results are also shown in the table.

                                      TABLE 2                                     __________________________________________________________________________            Composition (parts by weight)                                                 (A)                                                                           com-                                                                          ponent                       Properties of molded article                     Poly-               (D) component                                                                          Deflec-      ****                                ethyl-                    ***                                                                              tion         Sur-                                lene                      Na tem-                                                                              Molding                                                                            Heat                                                                              face                                tele-                                                                             (B) component   Na Na mon-                                                                             pera-                                                                             shrink-                                                                            shrink-                                                                           ap-                                                                              Tensile                                                                            Flexural            Example phtha-                                                                            Glass   (C) component                                                                         stea-                                                                            ben-                                                                             ta-                                                                              ture                                                                              age  age pear-                                                                            strength                                                                            strength           No.     late                                                                              fiber                                                                             Talc                                                                              DMT*                                                                              DET**                                                                             rate                                                                             zoate                                                                            nate                                                                             (°C.)                                                                      (%)  (%) ance                                                                             (kg/cm.sup.2)                                                                      (kg/cm.sup.2)       __________________________________________________________________________    Comparison  9                                                                         79.85                                                                             20  --  0.05                                                                              --  0.1                                                                              -- --  85 0.8  1.5 x  1200 1500                Comparison 10                                                                         69.85                                                                             30  --  --  0.05                                                                              0.1                                                                              -- --  83 0.8  1.5 x  1500 2100                Comparison 11                                                                         61  30  --  --  3   6  -- -- 215 1.0  0.11                                                                              o  1300 2000                4       62.9                                                                              35  --  2   --  -- 0.1                                                                              -- 213 1.3  0.12                                                                              o  1550 2200                5       66.7                                                                              30  --  3   --  -- 0.3                                                                              -- 220 1.4  0.10                                                                              o  1500 2100                                                  220                                         6       63.9                                                                              30  --  --  6   -- 0.1                                                                              -- 225 1.5  0.10                                                                              o  1400 2000                7       68.9                                                                              10  20  --  1   0.1                                                                              -- -- 200 1.4  0.12                                                                              o  1100 1400                8       66.7                                                                              30  --  --  3   -- -- 0.3                                                                              220 1.4  0.10                                                                              o  1500 2100                9       71.9                                                                              25  --  --  3   0.1                                                                              -- -- 215 1.3  0.12                                                                              o  1400 2000                __________________________________________________________________________     *, **, ***, ****: DMT, DET, Na montanate and surface appearance are as        defined in Table 1 above.                                                

It is apparent from Table 2 that the (C) component of less than 1 partby weight can not provide a high crystallinity and the (D) component ofmore than 5 parts by weight causes a lowering of strength. However, themolded articles of a composition falling within the scope of the presentinvention have a high crystallinity and a good surface appearance.

EXAMPLES 10-12 AND COMPARISON EXAMPLES 12-15

Pellets of polyethylene terephthalate having an intrinsic viscosity of0.64 and dried at 130° C. for 5 hours were uniformly mixed, in a V-typemixer, with glass chopped strands of a length of 3 mm, dimethylterephthalate or diethyl terephthalate and an ionic copolymer as shownin Table 3, in given proportions. The mixture was melt blended in anextruder of a diameter of 65 mm at a barrel temperature of 280° C. andformed into pellets by cooling and cutting the thread extruded from thedie. The pellets were then hot-air dried at 130° C. for 5 hours andinjection molded into test pieces on an injection molding machine of acapacity of 5 ounces provided with a mold for test pieces, under theconditions of a cylinder temperature of 270° C., a mold temperature of85° C., an injection pressure of 800 kg/cm², a cooling time of 20seconds and a cycle time of 35 seconds. The properties of the thusobtained articles are also shown in Table 3 below.

The ionic copolymer used in these examples was a copolymer of 90 partsby weight of ethylene and 10 parts by weight of methacrylic acid inwhich the carboxyl groups were neutralized by sodium ions. The meltindex of this copolymer was no more than 0.1 g/10 min. according to themethod of ASTM D1238-57T and the grain size was 300 to 500μ.

                                      TABLE 3                                     __________________________________________________________________________            Composition (parts by weight)                                                                             Properties of molded article                      (A)                         De-                                               component                   flection                                                                          Mold-                                         Poly-                 (D)   tem-                                                                              ing Heat                                                                              ****                                  ethylene              component                                                                           pera-                                                                             shrink-                                                                           shrink-                                                                           Surface                                                                            Tensile                                                                            Flexural            Example tereph-                                                                             (B) component                                                                         (C) component                                                                         Ionic ture                                                                              age age appear-                                                                            strength                                                                           strength            No.     thalate                                                                             Glass fiber                                                                           DMT*                                                                              DET**                                                                             copolymer                                                                           (°C.)                                                                      (%) (%) ance (kg/cm.sup.2)                                                                      (kg/cm.sup.2)       __________________________________________________________________________    Comparison 12                                                                         100   --      --  --  --    70  0.4 1.6 x     600 1000                Comparison 13                                                                         70    30      --  --  --    72  0.5 1.6 x    1500 2100                Comparison 14                                                                         66    30      --  --  4     70  0.4 1.6 o    1400 1900                Comparison 15                                                                         67    30      3   --  --    73  0.5 1.6 x    1500 2100                10      66    30      2   --  2     211 1.3 0.13                                                                              o    1400 2000                11      62    30      --  4   4     207 1.3 0.13                                                                              o    1500 2000                12      63    30      1   2   4     208 1.2 0.12                                                                              o    1500 2000                __________________________________________________________________________     *, **, ****: DMT, DET and surface appearance are as defined in Table 1.  

It is apparent from Table 3 that the absence of either the (C) componentor the (D) component provides a molded article of a low crystallinity,while the incorporation of the (C) component and the (D) component incombination according to the invention affords a molded article of ahigh crystallinity, a high deflection temperature, a low shrinkagefactor, and a good surface appearance.

EXAMPLE 13

100 parts by weight of polyethylene terephthalate pellets of anintrinsic viscosity of 0.72, dried at 140° C. for 4 hours, 42 parts byweight of glass chopped strands 3 mm long and 3 parts by weight ofdiethyl terephthalate were uniformly mixed in a tumbling barrel and themixture was formed into pellets in the same manner as in Example 10. Thethus obtained pellets were hot-air dried at 140° C. for 3 hours and thenuniformly mixed with 5 parts by weight, per 100 parts by weight of thepellets, of an ionic copolymer (grain size of about 500μ) of ahigh-pressure polyethylene grafted with 6 mol% of acrylic acid andneutralized by sodium hydroxide. The mixture was then subjected toinjection molding under the same conditions as in Example 10. The thusobtained article had a lustrous, excellent surface appearance as well asthe following properties.

    ______________________________________                                        Deflection temperature:                                                                            206° C.                                           Molding shrinkage factor:                                                                          1.3%                                                     Heat shrinkage factor:                                                                             0.13%                                                    Tensile strength:    1,300 kg/cm.sup.2                                        Flexural strength:   1,900 kg/cm.sup.2                                        Flexural modulus:    88,000 kg/cm.sup.2                                       ______________________________________                                    

EXAMPLE 14

64 parts by weight of polyethylene terephthalate pellets of an intrinsicviscosity of 0.64, dried at 130° C. for 5 hours, 10 parts by weight ofglas chopped strands 3 mm long, 20 parts by weight of talc (TalcumPowder PKN, sold by Hayashi Kasei Co., Ltd., Japan), 1 part by weight ofdimethyl terephthalate and 5 parts by weight of an ionic copolymer asused in Example 10 were mixed and formed into pellets in the same manneras described in Example 10. Then, the pellets were molded into anarticle as in Example 10. The thus obtained article had a lustrous,excellent surface appearance as well as the following properties.

    ______________________________________                                        Deflection temperature:                                                                             200° C.                                          Molding shrinkage factor:                                                                           0.8%                                                    Heat shrinkage factor:                                                                              0.1%                                                    Tensile strength:     1,100 kg/cm.sup.2                                       Flexural strength:    1,400 kg/cm.sup.2                                       ______________________________________                                    

We claim:
 1. A polyethylene terephthalate resin composition consistingessentially of (A) a polyethylene terephthalate resin having anintrinsic viscosity of 0.35 to 0.9 as measured in ortho-chlorophenol at35° C. and, per 100 parts by weight of the polyethylene terephthalateresin, (B) 5 to 200 parts by weight of an inorganic filler, (C) 0.1 to20 parts by weight of dimethyl terephthalate or diethyl terephthalateand (D) 0.01 to 5 parts by weight of a salt of a carboxylic acid with ametal of Group I or II in the periodic table or 0.1 to 10 parts byweight of an ionic copolymer of an α-olefin with a salt of anα,β-unsaturated carboxylic acid and containing an ion of a metal ofGroup I or II in the periodic table.
 2. A composition as claimed inclaim 1, wherein the (B) component is selected from glass fiber,asbestos, carbon fiber, potassium titanate fiber, mica, silica, talc,calcium carbonate, glass bead, glass flakes, clay and wollastonite.
 3. Acomposition as claimed in claim 1, wherein the (C) component iscontinued in an amount of 0.5 to 10 parts by weight per 100 parts byweight of the polyethylene terephthalate resin.
 4. A compound as claimedin claim 1, wherein the (D) component is selected from salts ofcarboxylic acids with metals of Groups I and II in the periodic table.5. A composition as claimed in claim 4, wherein the (D) component isselected from salts of metals of Groups I and II in the periodic tablewith aliphatic monocarboxylic acids, aliphatic monocarboxylic acids, andaromatic carboxylic acids.
 6. A composition as claimed in claim 5,wherein the aliphatic monocarboxylic acid is selected from acetic acid,propionic acid, caproic acid, palmitic acid, stearic acid, oleic acid,behenic acid, montanic acid, methacrylic acid and acrylic acid.
 7. Acomposition as claimed in claim 5, wherein the aliphatic dicarboxylicacid is selected from oxalic acid, adipic acid, succinic acid, sebacicacid, maleic acid and fumaric acid.
 8. A composition as claimed in claim5, wherein the aromatic carboxylic acid is selected from benzoic acid,terephathalic acid and phthalic acid.
 9. A composition as claimed inclaim 4, wherein the (D) component is contained in an amount of 0.05 to3 parts by weight per 100 parts by weight of the polyethyleneterephthalate resin.
 10. A composition as claim in claim 1, wherein the(D) component is selected from ionic copolymers of an α-olefin with anα,β-unsaturated carboxylic acid salt and containing an ion of a metal ofGroups I or II in the periodic table.
 11. A composition as claimed inclaim 10, wherein the ionic copolymer is selected from those having theunits of the following structural formula, ##STR3## in which R₁ ishydrogen, alkyl of 1 to 12 carbon atoms or phenyl, R₂ is hydrogen,methyl or ethyl, M_(e) is a metal atom of Group I or II in the periodictable, x and y are each independently an integer of 1 to 100, and n isan integer of 10 to 10,000.
 12. A composition as claimed in claim 10,wherein the ionic copolymer is selected from those of an α-olefin and anα,β-unsaturated dicarboxylic acid salt.
 13. A composition as claimed inclaim 10, wherein the ionic copolymer is selected from those having anα,β-unsaturated carboxylic acid ester chain grafted and then reactedwith an alkali metal hydroxide.
 14. A composition as claimed in claim10, wherein the ionic copolymer is selected from those having thefollowing units (a), (b) and (c), ##STR4## in which R₁, R₂ and M_(e) areas defined in claim 9, R₃ is hydrogen, methyl or ethyl, R₄ is hydrogenor alkyl of 1 to 12 carbon atoms, and x, y and z are each independentlyan integer of 1 to 100.